Flue baffle for gas-fired hot water tanks

ABSTRACT

A flue baffle for use in a hot water tank flue pipe which is disposed to be in contact with water contained in an inner tank of the hot water heater. A burner chamber is provided at a lower end of the inner tank. The flue baffle is comprised of an elongated rectangular metal strip which has a plurality of spaced circular metal discs disposed substantially transverse to the strip and to the longitudinal axis of the flue pipe. The metal discs are dimensioned to be spaced from an inner surface of the flue pipe. Two or more spacing nipples protrude from a circumferential outer edge of the circular metal discs and are spaced apart from one another for slight frictional engagement with the inner surface of the flue pipe to maintain a substantially constant circumferential passage between the circumferential outer edge of the discs and the inner surface of the flue pipe.

TECHNICAL FIELD

The present invention relates to a flue baffle for use in a hot water tank flue pipe through which flue gases from a burner chamber at the base thereof are discharged. The flue baffle creates turbulence and resistance of the flue gases to enhance heat exchange between the hot gases and the flue pipe and between the flue pipe and the water being heated in an inner tank and which is in direct contact with the exterior surface of the flue pipe.

BACKGROUND ART

It is known to mount a flue baffle inside a flue pipe of gas- or oil-fired water heater to retard the flow of exhausted hot gas from the lower burner chamber. As the gases escape upwards in the flue pipe they are retarded due to the resistance offered by the flue baffle to enhance heat exchange to transfer heat from the flue gases to the water surrounding a major portion of the flue pipe. At the same time, the flue gases are cooled as they rise up the flue pipe. The more efficient the flue baffle design is, the higher the thermal efficiency of the hot water heater becomes.

These baffles are normally elongated shaped elements which are suspended from the top end of the flue pipe and extend down the flue pipe. The shape of the baffle creates turbulence of the flue gases to slow down the flow of the gases going to an exhaust. One problem with existing flue baffles that are suspended, such as the flue baffle described in my U.S. Pat. No. 5,544,625 is that during transport of these hot water heaters the transport container containing the hot water heater can be laid down on its side in a transport vehicle, although this is not recommended. Installers of hot water heaters are usually plumbers, and because of vehicle sizes, often these are transported lying on their side. During transport the carrier vehicle is subjected to shocks due to bad road conditions and this is transmitted to the container. Also, the container can be mishandled. This often causes the flue baffle to be displaced within the flue pipe or be damaged. The result is that an improperly aligned or damaged baffle reduces the efficiency of the hot water heater as the flue baffle no longer provides the performance that it was designed to deliver when properly installed. Because these flue baffles are not inspected at the time of installation of the water heater due to the fact that they are held captive within the flue pipe inside the hot water heater and not accessible, damaged flue baffles are not detected and therefore the hot water heater does not render its full performance as it was designed to do. The net result is that it becomes more costly in gas or oil consumption to achieve the set water temperatures of the thermostat. Also, energy is wasted and polluted gases are exhausted in the atmosphere.

Another disadvantage of known flue baffles is that they are usually constructed of different parts which are assembled and welded together. Accordingly, this adds to the cost due to the amount of material used as well as the labour costs to construct the flue baffle.

SUMMARY OF INVENTION

It is therefore a feature of the present invention to provide a flue baffle which substantially overcomes the above-mentioned disadvantages of the prior art.

Another feature of the present invention is to provide a flue baffle which can be automatically constructed at low labour cost and/or low fabrication costs.

Another feature of the present invention is to provide a flue baffle which is entirely constructed from an elongated rectangular metal strip which is die-cut or laser-cut and then formed in forming dies without the need to assemble and weld parts.

According to the above features, from a broad aspect, the present invention provides a flue baffle for use. in a hot water tank flue pipe wherein the flue pipe is adapted to be in contact with water to be contained in an inner tank having a burner chamber at a lower end thereof. The flue baffle comprises an elongated rectangular metal strip having a plurality of spaced metal discs disposed substantially transverse to the strip and dimensioned to be spaced closely to an inner surface of the flue pipe. Two or more spacers protrude from a circumferential outer edge of the metal discs and are spaced-apart from one another for frictional engagement with the inner surface of the flue pipe to maintain a substantially constant passage between the outer edge of the metal discs and the inner surface of the flue pipe.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a simplified fragmented section view of a hot water tank having the flue baffle of the present invention secured in the exhaust flue pipe of the inner tank which is adapted to contain water to be heated;

FIG. 2 is a perspective view of the flue baffle of the present invention;

FIG. 3 is a side view of the flue baffle as seen from the side wall of the elongated rectangular metal strip illustrating the die-cut portions and the metal discs having been bent to their operating position;

FIG. 4 is a side view of FIG. 3;

FIG. 5 is a fragmented side view illustrating the relationship of the metal discs in relation to the inner surface of the flue pipe; and

FIG. 6 is a fragmented perspective view showing the construction of the support flange and the stiffening rib.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings and more particularly to FIG. 1, there is shown generally at 10 a hot water heater of the type provided with a gas or oil burner chamber 11 at a lower end of an inner tank housing 12. The inner tank housing 12 is supported on a base 13 and concealed within an outer thin metal casing 14. Insulating material 15 is disposed between the inner casing 12 and the outer casing 14.

As hereinshown a flue pipe 16 extends centrally within the inner tank housing 12 and exits the hot water heater through a coupling 17 at a top end to couple the flue pipe 16 to an exhaust duct 18. Although not shown, a fan is usually connected to the exhaust duct to draw the combustion gases through the flue pipe 16 to exhaust the combustion gases to atmosphere. As hereinshown, the flue baffle 20 of the present invention is suspended into the flue pipe 16.

Referring now to FIGS. 2 to 6, there will be described the construction and operation of the flue baffle 20 of the present invention. The flue baffle 20 is comprised of an elongated rectangular metal strip 21 which has a plurality of spaced-apart circular metal discs 22 which are disposed substantially transverse to the metal strip 21, as better seen in FIG. 4. These metal discs 22 are dimensioned to be spaced from an inner surface 23 of the flue pipe 16, as shown in FIG. 5.

As better seen in FIG. 2, the metal discs 22 are provided with two or more spacing nubs or nipples 24 which protrude from a circumferential outer edge 24 of the metal discs and extend a predetermined distance to create a substantially constant circumferential passage 25 between the circumferential outer edge 24 and the inner surface 23 of the flue pipe 16, as can be seen from FIG. 5. This permits the hot flue gases to flow about the metal discs 22 which are positioned along a major portion of the flue pipe 16, in a substantially uniform and constant manner. This flow is illustrated by arrows 26 in FIG. 5.

As also shown in FIG. 2, there are four of these spacing nipples 24 positioned about the outer circumference of each disc and substantially aligned on diametrical axes of the discs with these diametrical axes extending transverse to one another. The discs are dimensioned such that the nipples are disposed for very slight frictional contact with the inner surface 23 of the flue pipe whereby to provide this constant circumferential passage 25 about all of the discs along the entire length of the flue baffle 20.

As better shown in FIGS. 2 and 3, the circular metal discs 22 are integrally formed with the elongated rectangular metal strip 21 and these are die-cut or laser-cut into that metal strip as semi-circular disc sections 22′ and 22″ and then bent at right angles to position the metal disc sections transversely to the longitudinal axis of the metal strip. As hereinshown, these two semi-circular disc sections 22′ and 22″ are disposed on a respective side of a transverse diametrical rib section 27 formed in the strip and acting as supports and braces. Each disc section 22′ and 22″ is bent at a right angle from a respective edge of the rib section 27 on a respective one of opposed sides of the metal strip, as is illustrated in FIG. 4. As can be seen, these semi-circular disc sections 22′ and 22″ are slightly offset from one another and spaced by the interconnecting rib 27. As shown in FIG. 2, the nipples are so disposed that there are two spacing nipples projecting from each of the two semi-circular disc sections 22′ and 22″.

As can be seen from FIGS. 2, 3 and 6, the elongated rectangular metal strip is further provided with elongated stiffening ribs 28 on opposed longitudinal side edges thereof. These stiffening ribs are formed by a folded-over edge strip section 28′ as better seen from FIG. 6. Accordingly, the discs are rigidly connected to a sturdy baffle frame formed integral with the metal strip.

The elongated rectangular metal strip 21 is further formed with opposed support shoulders or flanges 29 which project from opposed elongated side edges at a top support end of the elongated rectangular metal strip. These support flanges 29 are formed when the folded over edge strip sections 28′ are bent over the elongated rectangular metal strip and terminate from the top end 30 thereof. It is pointed out that the bending of the semi-circular discs 22′ and 22″ are formed in a jig as well as the folding over of the edge strip section 28′ to form the stiffening rib 28. Also, the slitting of the flat metal strip is effected by metal stamping or laser cutting, as previously described. Accordingly, one can appreciate that the flue baffle of the present invention is very economical to produce having a substantial reduction in labour cost as there are no parts to assemble or weld together.

The outwardly projecting flanges 29, at the top end 30 of the elongated rectangular metal strip 21 constitute a support flange on opposed sides thereof for suspending the strip from a top end 19 of the flue pipe 16, as illustrated in FIG. 1.

The flue baffle 20 of the present invention is fabricated from an 18 gauge steel sheet or any suitable material with negligible material waste as these elongated rectangular metal strips are cut side-by-side in a sheet of steel material suitable for use at the temperatures that are common in flue pipes of these water heaters. It can be appreciated that as the hot flue gases 26 escape up the flue pipe 16 they are caused to be retarded and turbulate between these metal discs 22 and are slowed down to provide heat exchange with the water 9 in contact about the flue pipe to further heat this water. Of course, the hottest temperature is in the combustion chamber 11 where the bottom wall 8 of the inner tank delineates the shape of the combustion chamber upper wall and this bottom wall 8 is in direct contact with the flames and in heat exchange with the water 9 in the inner tank.

Another advantage of the baffle is to retard heat loss when the flue pipe cools down and a reverse effect occurs in that the temperature of the hot water then loses heat through the flue pipe. This baffle accordingly further retards heat escaping through the flue pipe in such conditions. By maintaining the metal discs centered within the flue pipe, a constant circumferential passage 25 is maintained throughout the flue baffle and this provides for a very efficient and constant thermal efficient water heater. The spacing nipples thus contribute to this constant efficiency and also prevents the metal discs or baffle discs to be displaced and damaged during transport due to mishandling of the hot water heater and preventing damage to the metal disc. With the prior art baffles of the type using twisted baffle side walls or plates, the thermal efficiency varies greatly between hot water heaters equipped with the same baffle design due to misalignment or damage thereto.

It is within the ambit of the present invention to cover any obvious modifications of the preferred embodiment describe herein provided such modifications fall within the scope of the appended claims. 

1. A flue baffle for use in a hot water tank flue pipe wherein said flue pipe is adapted to be in contact with water to be contained in an inner tank having a burner chamber at a lower end thereof, said flue baffle comprising an elongated rectangular metal strip having a plurality of spaced metal discs disposed substantially transverse to said strip and dimensioned to be spaced closely to an inner surface of the flue pipe, and two or more spacers protruding from a circumferential outer edge of said metal discs and are spaced apart from one another for frictional engagement with the inner surface of the flue pipe to maintain a substantially constant passage between said outer edge of said metal discs and the inner surface of the flue pipe.
 2. A flue baffle as claimed in claim 1 wherein said metal discs are circular metal discs integrally formed with said elongated rectangular metal strip and disposed at right angles to said metal strip.
 3. A flue baffle as claimed in claim 2 wherein said circular metal discs are each formed by two semi-circular disc sections cut from said metal strip, each disc section being disposed on a respective side of a transverse diametrical rib section, each disc section being bent at right angles from a respective edge of said rib section and on a respective one of opposed sides of said metal strip, said disc sections forming a substantially circumferential and constant passage about each said discs.
 4. A flue baffle as claimed in claim 3 wherein said spacers are spacing nipples integrally formed with said semi-circular disc sections, there being two of said spacing nipples projecting from each said two semi-circular disc sections.
 5. A flue baffle as claimed in claim 2 wherein said elongated rectangular metal strip has a stiffening rib formed along opposed elongated side edges thereof by a folded-over edge strip section, said edge strip sections and said transverse diametrical rib section forming a rigid support frame.
 6. A flue baffle as claimed in claim 2 wherein said elongated rectangular metal strip has opposed support flanges projecting from opposed elongated side edges thereof at a top end of said elongated rectangular metal strip.
 7. A flue baffle as claimed in claim 5 wherein said folded-over edge strip section extends from a bottom end of said elongated rectangular metal strip and terminates a short distance from a top end thereof to define an outwardly projecting flange section at said top end, said outwardly projecting flange section constituting a support flange for suspending said strip in the flue pipe.
 8. A flue baffle as claimed in claim 2 wherein said flue baffle is a one-piece flue baffle constructed entirely from said elongated rectangular metal strip.
 9. A flue baffle as claimed in claim 3 wherein said semi-circular disc sections are cut from said elongated rectangular metal strip by one of metal stamping or laser cutting.
 10. A flue baffle as claimed in claim 1 wherein said elongated rectangular metal strip is constructed from 18 gauge steel sheet material. 